Question

What is the sample space of rolling a 6-sided die?

Answer 1

Its {1,2,3,4,5,6}
which is actually a set of all the possible outcomes as the definition of sample space specifies.

When you roll a 6 sided dice, number of dots on uppermost face is called as outcome. Now, whenever a dice is rolled we can get either 1, 2,3,4,5 or 6 dots on the upper most face..that is now outcome.

So experiment here is "Rolling a 6 faced dice" and list of possible outcomes is "{1,2,3,4,5,6}".

Sample space by its definition is list of all the possible outcomes of an experiment.
So answer to your question is
S={1,2,3,4,5,6}

I hope its clear.